Chaco Canyon, Its World, and Ours

Archive for April, 2010

In a previous post discussing the spread of the bow and arrow through North America, I said that it had just barely reached central Mexico by the time of Spanish contact and hadn’t reached the Maya area at all. That was based on the impression I had gotten from Steven LeBlanc’s book on Southwestern warfare, but it turns out that it isn’t really true. The bow and arrow reached Mesoamerica at some point in the Late Postclassic, and was used by both the Aztecs and Mayans when the Spanish first encountered them, although it did not displace the atlatl, which retained its widespread use and prestigious cultural position. The bow and arrow also spread further, into South America, where it became widely used in the Amazon but remained somewhat marginal in the Andes, as it did in Mesoamerica. I haven’t been able to find any firm dates for the first appearance of the bow and arrow in South America. If it came there from Mesoamerica it must have been pretty late in the prehistoric period. I have seen some tantalizing suggestions that it was present considerably earlier, which would complicate the picture considerably. I’m continuing to look into this issue.

Partly Walled-Up T-Shaped Doorway at Chetro Ketl

In some ways, the wider spread of the bow and arrow is even more interesting than my original impression that its distribution was due mainly to slow diffusion. If Mesoamerican societies were unaware of the technology, or if it had just been introduced and had not been fully integrated into the established weaponry system, that would easily explain why they were still relying primarily on the atlatl when the Spanish encountered them. Since it turns out that they were in fact familiar with the bow and arrow, and had been for at least a little while (long enough for the Aztecs to incorporate it into their military system), the fact that they didn’t seem to consider it obviously superior to the atlatl becomes more mysterious. Many archaeologists seem to think of the superiority of the bow and arrow to the atlatl as so obvious that they assume it would have immediately taken over in an area as soon as it was introduced. This may have happened in some areas, and it certainly did eventually take over entirely in, e.g., the Southwest, but elsewhere the situation is not so clear, and in some areas use of both atlatl and bow may have gone on for a very long time. In Mesoamerica the enormous cultural significance of the atlatl was probably one major reason for this, and something similar may have happened in some other areas. Of course, making any hypotheses about the shift from atlatl to bow and arrow requires the ability to tell when exactly the bow and arrow was introduced to a given area, which is trickier than it sounds. But that’s a topic for a later post.

Everyone is familiar with the bow and arrow, but what on earth is an atlatl? Although this implement was once used all over the world and was an important part of life, in most areas it was replaced by other weapons so long ago that it is no longer remembered, and most people today have never even seen one. In a few areas, like Mesoamerica and Australia, use of the atlatl continued up to (and beyond) European contact, but throughout most of the world it is known today only from archaeological specimens and reconstructions by interested hobbyists, who are often archers. One interesting aspect of the study of the atlatl in American archaeology has been the important role played by these amateurs, who have often demonstrated through experiments that the conclusions of archaeologists about the use of atlatls were clearly mistaken.

Slickrock Sandstone, Kayenta, Arizona

An atlatl is basically a device for assisting in throwing a spear. They are almost always made of wood, which means that archaeologically they rarely survive intact except in very dry areas like the Southwest. They are typically about half a meter long, and take the form of a long, thin board with a shallow groove running down the middle and a hook or spur at one end to hold the butt end of the spear. Southwestern examples typically have leather finger loops at the point where the atlatl would be held. Occasional examples in other areas, as well as the presence of associated artifacts made of more durable materials, have demonstrated the use of the atlatl throughout the Americas, but understandings of how these atlatls were made and how they functioned have been heavily reliant on Southwestern examples, particularly the exceptionally well-preserved ones found in Basketmaker II rockshelters in the Kayenta area by Alfred Kidder and Samuel Guernsey in the early twentieth century. There is also a considerable amount of ethnohistoric data on the use of the atlatl in Mesoamerica, which is helpful in understanding atlatls elsewhere but must be used cautiously because Mesoamerican atlatls are typically rather different in form from Southwestern ones, and there may have been corresponding functional differences as well.

Sandstone Formations, Kayenta, Arizona

The precise way the atlatl functioned has not always been apparent to archaeologists, who have in general been notably disinclined to experiment, and amateur experimenters using replicas of archaeological atlatls have made important contributions to understanding this. One such amateur was Calvin D. Howard of Houston, who published a useful paper in American Antiquity in 1974 reporting on his experiments and explaining how an atlatl actually works. Here is his basic point:

Surprisingly, considering popular consensus, the atlatl is not a catapult or “flipping” device. In fact, during a proper throw, the spur at the aft end of the atlatl reaches no greater elevation than that reached by the handle at the forward end. The spur does not swing upward in an arc, but merely “follows through” in the original portion of the spear’s flight path. Therefore, the most expeditious way to learn the use of the atlatl is to throw the spear with the atlatl exactly the way it is thrown without it.

The atlatl provides greater thrust than the unaided hand simply because it remains in contact with the spear during a greater portion of the total thrust than does the hand.

He later elaborates on this:

When a spear is thrown with the atlatl, the thrust begins with the hand at the same location behind the thrower, that is, as far back as his reach allows. The hand is moved forward along the same necessary straight path toward the target. When the arm nears the outstretched position-the point of release for the hand-held spear-the atlatl is still in contact with the spear. As the hand and the forward end of the atlatl begin the downward curve, the aft end, with the spur still in contact with the spear, continues on the straight thrust line. The atlatl is therefore converting downward curving thrust to straight forward thrust, thereby prolonging contact between spear and thrust. The spear thus receives a greater portion of the total thrust energy expended.

I haven’t used an atlatl myself, so I just have to trust Howard on this. He also argues, based on his own experiments, that longer spears are more affected by the increase in thrust given by the atlatl relative to a bare-handed throw, and that the increase in thrust due to the atlatl is about 60%, which makes it a very useful device indeed. He also says that his experiments have shown that atlatl “weights,” stone objects found lashed to most Southwestern archaeological atlatls but unknown in Mesoamerican examples, provide no additional benefit in terms of thrust, and in fact reduce the effectiveness of the atlatl. The function of these “weights” has been one of the most puzzling issues in the study of atlatls, and I’ll address it in more detail later.Howard, C. (1974). The Atlatl: Function and Performance American Antiquity, 39 (1) DOI: 10.2307/279223

I’ve decided to do a series of posts on the issue of prehistoric weaponry and the spread of the bow and arrow through North America. This is an important topic, and one that has received a considerable amount of attention from archaeologists and others over the past century. Despite that long history of research, there are still a lot of unresolved questions about this, and it has been a highly contentious issue in some circles.

Petroglyph Panel at Atlatl Rock, Valley of Fire State Park

To frame the issue, and to demonstrate its importance to Chaco specifically and Southwestern archaeology more generally, I’d like to go back to a topic I haven’t discussed much lately: warfare, and in particular Steven LeBlanc’s book on warfare in the prehistoric Southwest. This is a controversial issue, although most Southwestern archaeologists seem to be coming around to the view that warfare was important even if they don’t see it as central the way LeBlanc does. Leaving all that aside for now, however, LeBlanc also provides a useful model for the spread of prehistoric weaponry in the Southwest that clearly shows the importance of the bow and arrow. He uses weaponry type as one of the defining features of the three periods into which he divides Southwestern prehistory from the perspective of warfare. Each period is marked by the adoption of a new type of weapon, in each case more effective than the last. The periods don’t quite line up with the probable dates of adoption of the new weapons, however, which suggests that there was more going on than mere technological developments. This has to be the case, actually, because LeBlanc’s middle period (AD 900 to 1150, which roughly coincides with the Chacoan era) is marked by a noteworthy decrease in evidence for warfare despite coming not long after the introduction of the bow and arrow to the Southwest.

Arrowheads at Chaco Visitor Center Museum

LeBlanc’s early period, which runs from the first settlement of the Southwest up to around AD 900, was marked by endemic warfare among small groups using atlatls. The atlatl, known by various other names such as “spear-thrower” but in this context usually called by its Nahuatl name, is a tool used to launch spears (often called “atlatl darts”) with greater force and to a greater distance than is possible with the unaided hand. It is found in every inhabited part of the world starting in very early times, and probably dates far back into the Paleolithic Era, before the spread of modern humans throughout the world. It was thus presumably known to the earliest inhabitants of both the Americas in general and the Southwest in particular. Most archaeologists generally think of the atlatl in a hunting context, and it would certainly have been used for hunting. LeBlanc, however, points out that any weapon used for hunting would also be useful in war, and since he proposes that war was going on constantly during his early period, it stands to reason that the main weapon would have been the atlatl. He also argues that the large wooden club-like artifacts found in sites of this era, often known as “rabbit sticks” and associated with hunting of small game, were instead “fending sticks” used to deflect atlatl darts. I’m not sure I buy this, but it does make sense that people fighting with atlatls would want to do something to defend themselves against darts coming at them and the sticks would work. Support for the idea that the atlatl was a weapon of war in addition to a hunting tool comes from Mesoamerica, where military use of the atlatl came to be a major feature of the very warlike societies there.

"Rush to the Rockies" Sign, Trinidad, Colorado

At some point near the end of LeBlanc’s early period, a new weapon system appeared in the Southwest: the bow and arrow. The spread of the bow and arrow is fascinating, since unlike almost all other examples of diffusion of ideas and technologies through North America it came not from the south but from the north. It originated somewhere in Eurasia very early on, and then spread very slowly to the Bering Strait, and from there on down the continent. The most interesting part, and something that I’ll be addressing in more detail in subsequent posts in this series, is that it’s possible to track the movement of the bow and arrow south from the Arctic by looking at the first appearance of it in rock art and artifact assemblages at sites in various areas. It reached the Southwest sometime around the Pueblo I period and immediately replaced the atlatl as the preferred weapon for both hunting and (presumably) war. It then continued to spread to the south, but for some reason it didn’t really catch on in Mesoamerica the way it had in most of the areas to the north. This may have been because of the cultural importance of the atlatl, but it could also have been because it had just barely reached central Mexico when the Spanish arrived and threw everything into chaos. In fact, I’m not entirely sure it got as far as central Mexico at all; I haven’t found any sources that discuss this precise issue, although there’s been so much attention paid to Aztec warfare that I’m sure it’s discussed somewhere. It definitely never reached the Maya. All these Mesoamerican groups were still using the atlatl as their primary weapon when the Spanish showed up with guns.

Sign for Atlatl Rock, Valley of Fire State Park

LeBlanc’s late period, from AD 1250 until Spanish contact, is associated with the use of the recurved bow, which is a more powerful weapon than the self bow that had been used before and may have had something to do with the immense amount of violence that is evident in the Southwest during this period. This is an interesting topic in its own right, but I’m not really going to go into it in this series, which is more focused on the initial adoption of the (self) bow and arrow in various parts of North America.

Stairs to Atlatl Petroglyph at Atlatl Rock, Valley of Fire State Park

Okay, so, that seems pretty straightforward, doesn’t it? If there is clear evidence for the spread of the bow from Asia into North America and then south, where’s the controversy? Well, I was a bit too glib above in saying that the spread of the bow and arrow can be easily tracked by looking at its first appearance in the archaeological record in various areas. The general picture still holds, I think, but the details are muddled, and there is considerable disagreement among archaeologists about what counts as evidence for the introduction of the bow and arrow in some regions. The main reason for this is that in most areas, the actual bows and arrowshafts don’t survive, since they’re made of perishable materials. Nor, for that matter, do atlatls, at least in their entirety. The main remains of both types of weapons are the projectile points, which are usually made of hard stone. Atlatls also can have parts attached to them (known as “spurs” and “weights”) which are made of harder materials like stone or bone, and these can survive even when the wooden body of the atlatl doesn’t, although they can be hard to recognize on their own. In general, then, dating the replacement of the atlatl by the bow and arrow requires the ability to differentiate between dart points and arrowheads. Since atlatl darts are spears, it is generally thought that they should have bigger, heavier points than arrows, and size is indeed one criterion used to differentiate between the two types of point. This is controversial, however, for reasons that I’ll go into in future posts.

Hollow Mountain Gas Station, Hanksville, Utah

The entry of the bow and arrow into the Southwest, by the way, is dated much more precisely than is the case in other reasons, primarily because the much better preservation conditions in many Southwestern contexts mean that actual atlatls, darts, bows, and arrows do often survive, which allows a much better understanding of what they were like than is possible elsewhere. This has been very helpful in getting a sense of the situation elsewhere, although other factors mean that it can’t answer all the questions about those other places. This importance of the Southwest to understanding the spread of the bow and arrow, despite not being the area where that spread either began or ended, makes this blog a good place for an examination of the issue, as does the importance of that spread to understanding cultural developments in the Southwest. Those developments seem to have something to do with changes in weaponry, although the precise connection is difficult to discern.

Speaking of West Mexico, as I have been lately, Mike Smith links to a very interesting article on the Lake Pátzcuaro Basin Archaeological Project‘s work at an urban (or proto-urban) site that predates the Tarascan imperial capital at Tzintzuntzan. As I’ve been saying, I think a lot of recent research like this is showing that West Mexico was a much more important cultural area within Mesoamerica than people have realized. This particular site is especially interesting since it appears to date to between 1000 and 1350 AD, which makes it contemporaneous with Chaco. One of the frustrating things about trying to trace the specific Mesoamerican contacts of the Chacoans is that the Chacoan era corresponds to the Mesoamerican Early Postclassic, which has received much less attention from archaeologists than the Classic and Late Postclassic periods before and after it. It’s hardly surprising that so much research would focus on impressive sites of the Classic (Teotihuacan, Tikal and the other Maya cities, and other large urban centers throughout Mesoamerica) and Late Postclassic (Tenochtitlan and the smaller Aztec cities), but while some Early Postclassic centers are fairly well-known (e.g., Chichen Itza, Tula, and Cholula) they have tended to be overshadowed by the other sites. West Mexico is particularly poorly understood in this period, which is particularly unfortunate for Chacoan studies because it was almost certainly the part of Mesoamerica with the greatest direct influence on the Southwest. This pre-Tzintzuntzan city, then, is very important to understanding Chaco, and it’s good to see that it’s getting some attention.

Malpais Nature Trail Sign at Valley of Fires, Carrizozo, New Mexico

Another thing to note, although I’m not sure how important it actually is, is that the Lake Pátzacuaro Basin is dominated by volcanic geology (malpaís). In Mesoamerica the main advantage of this kind of location would probably have been control over the obsidian sources associated with volcanoes. It’s been suggested that the rise of Teotihuacan had to do with its control of local obsidian, and the Tarascans seem to have had a big role in the obsidian trade as well. Obsidian was highly valued by Mesoamerican cultures, so control over the supply of it was a big deal. (Interestingly, obsidian is vanishingly rare at Chaco, despite the many Mesoamerican traits there and the presence of several obsidian sources within the plausible Chacoan sphere of influence.) The Tarascans were also noted for their use of copper, which may have been a bigger deal, since there are many sources of obsidian in Mesoamerica but knowledge of copper metallurgy didn’t begin spread from of West Mexico until quite late in the Postclassic. Copper bells, of course, are among the best-known artifacts of definite Mesoamerican origin found at Chaco. It all presumably fits together somehow, but it’s hard to tell exactly how.

Most research on human-environment interactions focuses on large-scale changes in environmental conditions over long periods of time (by human standards, at least). There are good reasons for this, especially when applied to prehistory, most importantly that there are a lot of potential data sources for environmental conditions that can be correlated with cultural chronologies to identify possible relationships between the two. A lot of research in the Southwest along these lines has sought to correlate periods of higher and lower average rainfall, readily apparent in tree-ring records, with population increases, decreases, and movements, as inferred from the number and types of archaeological sites in a given area, which conveniently can be dated with those very same tree-ring chronologies. Jeff Dean at the University of Arizona’s Laboratory of Tree-Ring Research has been a major figure in this sort of research for a long time, and it’s resulted in a lot of interesting insights and theories about Southwestern prehistory.

"Squeeze-Up" at Sunset Crater National Monument

As we’re seeing right now in Iceland, however, there is another type of environmental event that can affect human societies: a short, intense, unexpected, and uncontrollable catastrophe like an earthquake or a volcanic eruption. These are generally harder to see in the paleoclimatological record, and as a result they are hard to correlate with cultural changes. Volcanoes themselves, however, are an exception to this invisibility, since they spew out all kinds of ash and lava that have very visible effects on the local geology. In many cases these can be dated by radiocarbon or other methods and correlated with events in the societies of the people living in the area. One very good example of this is found in Alaska among the northern Athapaskans. Another is closer to home, as it were, from the perspective of this blog: Sunset Crater.

Sign Explaining "Squeeze-Up" at Sunset Crater National Monument

Sunset Crater is northeast of Flagstaff, Arizona. It is the most recent of the San Francisco Peaks to erupt, and the only one to erupt during the time that humans have occupied the area. It erupted sometime in the mid-to-late eleventh century AD; the date 1064 AD gets thrown around a lot, based on some tree-ring samples at Wupatki that showed odd ring patterns in the few years after that, but this dating has been questioned and the general consensus is only that the eruption occurred sometime around this time, based on the (often quite large) deposits of ash found in sites from this period. Note that this is during the height of the Chacoan era. The eruption may have been visible at Chaco itself, and it was certainly visible at some of the outlying Chacoan sites, so the Chacoans, along with everyone else in the region, would definitely have been aware of the events even though the immediate area shows little to no Chacoan influence. It’s not clear how long the eruption lasted. Eruptions of cinder cone volcanoes can potentially go on intermittently for decades, although they can also be much shorter. Sunset Crater could have kept erupting for as long as 100 years or even 200, but more data are needed to determine this more precisely.

Sandstone and Igneous Masonry at Nalakihu, Wupatki National Monument

One theory about the effect of the eruption on human societies, first formulated by Harold Colton of the Museum of Northern Arizona in the 1930s, is that while the initial eruption was devastating to the small local population, the layer of ash that the eruption laid down turned out to be an excellent mulch, holding in much-needed moisture in this dry area and making agriculture much more productive, which spurred a massive influx of population to places like Wupatki that had been covered by ash and led to substantial cultural changes. This theory has since been challenged, and there is no real consensus today on what effect the eruption had on cultural dynamics in the area. It is highly unlikely, however, that it had no effect. A volcanic eruption is a big disruption to existing patterns of living.

Lava at Valley of Fires Recreation Area, Carrizozo, New Mexico

One interesting and concrete manifestation of the effects the eruption may have had on local people comes from an interesting paper (which is my source for most of the general information about Sunset Crater above) on some building stones found at a nearby habitation site that show clear imprints of corncobs in them. The authors conclude that this could pretty much only result from people deliberately going to places where lava was coming out, probably small features known as hornitos that would have been easily approachable, and putting in offerings of corn cobs to let the lava run over them, then after the lava cooled taking the rocks back to the site (which is a few miles away) and forming them into building blocks with distinct corncob impressions. This would have been a lot of work, so it’s pretty apparent that it had a lot of cultural importance in some way.

Post Office, Carrizozo, New Mexico

Another interesting cultural connection to volcanoes is suggested in this article in the Alamogordo Daily News (via Southwestern Archaeology Today) about a salvage archaeology project south of Carrizozo, New Mexico, an area of considerable volcanic activity, that uncovered a large site that seems to probably date to around AD 900 to 1100, again during the Chacoan period. This era is not very well-understood in this part of New Mexico, which was occupied by the Jornada Mogollon who may have later played an important role in the origins of the kachina cult. One of the crew members, a woman from Santa Clara Pueblo, mentions that “where the lava comes out … represents the underworld.” The article is kind of confusingly written, so it’s not clear exactly what she means by that, but it’s a really interesting clue to the importance of volcanoes to Pueblo people. I don’t know much about the dating of the lava flows around Carrizozo, so I don’t know if the Jornada Mogollon would have been around to see the actual lava come out, but even if they didn’t they may have regarded certain vents and other features with reverence. They certainly used the resulting igneous boulders as a medium for their extensive and innovative petroglyphs.

Carrizozo Trading Company Sign, Carrizozo, New Mexico

I’m increasingly coming to think that the importance of sudden, catastrophic events like volcanic eruptions has received too little attention among archaeologists. Certainly long-term climatic changes are important, as are culture, political, and historical factors, but a catastrophe has a way of forcing changes very suddenly that may shed light on some of the more puzzling changes in the archaeological record. Something to think about as we watch the effects of a volcano in Iceland on people throughout northern Europe and beyond.Elson, M., Ort, M., Hesse, S., & Duffield, W. (2002). Lava, Corn, and Ritual in the Northern Southwest American Antiquity, 67 (1) DOI: 10.2307/2694881

Continuing my recent agriculturekick, I thought I’d just point to an interesting post from a little while back talking about modern agriculture, private property, contract archaeology, resource protection legislation, and the tendency for people (even archaeologists!) to not understand how they all relate to each other in practice. I don’t have much to add, but it’s a nice post and well worth reading.

I’ve talked a bit about Jane Hill‘s theory that agriculture was introduced to the Southwest by a migration of speakers of Uto-Aztecan languages from Mesoamerica, which she supports mostly through somewhat unconvincing linguistic evidence. A recent paper in, yes, PNAS offers a strong set of counterarguments to Hill’s theory, and offers an alternative theory in which maize agriculture gradually diffused north from Mesoamerica through a chain of hunter-gatherer groups in western Mexico speaking Southern Uto-Aztecan languages.

"Plateau Country Trees" Sign, Pipe Spring National Monument

The authors, who include some fairly prominent Southwestern archaeologists, frame their argument explicitly in opposition to Hill’s, and they begin by pointing out the weakness of her linguistic arguments for a set of maize-related terms in Proto-Uto-Aztecan, which is a crucial part of her theory that the family originated in Mesoamerica and spread northward. They also point to DNA evidence showing that Uto-Aztecan speakers in the Southwest and in Mesoamerica genetically resemble surrounding populations speaking other languages much more than they resemble each other, which mostly suggests a long period of interaction and intermarriage among neighboring groups on both ends, implying that whatever migration occurred probably happened far in the past and not providing any particular evidence for which way it went. This evidence is interesting, and I had not seen it before. I think it may be the strongest evidence against Hill’s theory, which only works with a relatively recent migration from south to north that would presumably show up in the genetic evidence.

Sign Describing Pinyon and Juniper, Pipe Spring National Monument

The other evidence they present, both on behalf of their own theory and against Hill’s, is quite a bit weaker, I think. They argue for a Uto-Aztecan Urheimat in the Great Basin at the very opposite end of the current distribution of the family from Hill’s proposal of western Mesoamerica, and for a very early dispersal of the family to the south starting around 6900 BC. They make these proposals based on evidence from the suite of terms for animals and plants that can be reconstructed for Proto-Uto-Aztecan. As Hill noted in her papers, this set of flora and fauna is found throughout most of the current range of the languages, from the Southwest down far into Mexico, and so it doesn’t directly provide much evidence for the initial location of the protolanguage. The authors of this paper, however, argue from negative evidence that it can be pinpointed to a northerly location at an early time. Their reasoning is interesting: apparently two terms that cannot be reconstructed for Proto-Uto-Aztecan, even though the items they refer to occur almost everywhere Uto-Aztecan languages are spoken, are “pinyon” and “oak.” They take this to mean that the protolanguguage was spoken in a context where there were no pinyons or oaks, and the only place they can find this to be the case is the west-central Great Basin between 9700 and 6900 BC. Around 6900 BC conditions in the Great Basin became considerably drier, and the authors point to this event as the catalyst for the initial breakup of the Proto-Uto-Aztecan speech community with the ancestors of what would become the Southern Uto-Aztecan languages migrating south in search of wetter areas, eventually ending up in the southern Southwest and northwest Mexico, with the ancestors of Northern Uto-Aztecan speakers remaining in the north at least until pinyons began to spread northward around 5500 BC. Later, when maize agriculture began to diffuse northward from Mexico, the Southern Uto-Aztecan groups were arranged in a long continuum along the Pacific coast and the adjacent mountains, and they passed the maize plant and knowledge of its cultivation steadily northward until it reached the southern Southwest and was adopted by local hunter-gatherer groups there, only some of which spoke Uto-Aztecan languages. The earliest well-dated maize remains in the Southwest (mostly from the Tucson area) date to around 2100 BC, so the posited Southern Uto-Aztecan continuum must have been in place by then, which would definitely require a very early date for the initial breakup of the protolanguage if indeed it originated in the north.

Live Oak, Pipe Spring National Monument

This all makes sense, as far as it goes, but it’s really just as speculative as Hill’s theory, and as the authors point out what’s really needed to make further progress in understanding this issue is more archaeological data on the area in between Mesoamerica and the Southwest, i.e., the area through which maize would have to have passed on its way north. They do point out one important strike against Hill’s theory, which is the lack of any clear similarities in material culture between the earliest agricultural sites in the Southwest and contemporary agricultural sites in Mesoamerica, which may argue for a diffusion of agriculture but could possibly also just mean that the migration of agriculturalists, whether or not they spoke Uto-Aztecan, took place much earlier. Indeed, this paper appears to put the starting point for the spread of maize at the place and time of the earliest macrobotanical evidence for maize (that is, the earliest actual cobs found in the archaeological record), which comes from Guilá Naquitz Cave in Oaxaca around 4300 BC. This is a very odd choice of place and time, however, since it is increasingly clear from starch grain and phytolith evidence, as well as genetics and the distribution of wild teosinte varieties, that maize was initially domesticated considerably earlier and further west, being definitely present in the Rio Balsas area of Guerrero by 6700 BC. It’s particularly odd since they do in fact cite one of the recent papers presenting this evidence. Since maize would certainly have had to initially diffuse from West Mexico to Oaxaca, there’s no reason to think there’s anything special about Oaxaca or 4300 BC from the point of view of the history of maize agriculture in general; this just happens to be the oldest setting with sufficiently good preservation to allow macrobotanical evidence to survive. Instead, any diffusion of maize to the Southwest would certainly have begun in West Mexico, and could have begun as early as 6700 BC. A migration at this point would be very difficult to detect in the archaeological record, and the presence of maize cultivation in the Southwest this early would also be very difficult to see. The paper’s authors do acknowledge the possibility that maize cultivation had been going on in the Southwest before the earliest evidence of it so far discovered, but they don’t seem to really grapple with the implications of that for their theories.

Trucks at Rest Stop, Luning, Nevada

In general, I find the kind of arguments used in this sort of research interesting but not very conclusive. The use of reconstructible terms for flora and fauna has a long history in historical linguistics, but it has not actually been very successful in pinpointing the original locations of protolanguages. One reason for this is that terms change over time, and it’s not always clear if a given word, even if shared by most languages in a family, has the same meaning now that it had in the protolanguage. Negative evidence of the sort used here, in particular, is problematic. What if Proto-Uto-Aztecan did actually have a term for “pinyon” that just happened to be lost or used for another plant in several of the daughter languages? This is very much a possibility, and it’s basically impossible to judge its likelihood based on available evidence. Also, while using paleoclimatological data to give dates to linguistic events is an interesting idea, I do think this paper goes a bit too far with it. There are a lot of assumptions behind the idea that a drought in the Great Basin around 6900 BC caused the breakup of Proto-Uto-Aztecan, and given that this date is much earlier than all other dates that have been proposed for this event, those assumptions really need to be critically examined.

Pinyon Trees, Pipe Spring National Monument

Nevertheless, for all its flaws, this is an interesting and important paper, particularly in the way it seeks to incorporate more lines of evidence into the ongoing debate over the introduction of agriculture to the Southwest. There has been so much research on this topic lately, much of it overturning long-held assumptions, that it is good to see some attempts to tie it all together, even if they are ultimately unconvincing.Merrill, W., Hard, R., Mabry, J., Fritz, G., Adams, K., Roney, J., & MacWilliams, A. (2009). The diffusion of maize to the southwestern United States and its impact Proceedings of the National Academy of Sciences, 106 (50), 21019-21026 DOI: 10.1073/pnas.0906075106